Something sinister is growing in Academy City. The shadows are filled with whispers of a project to clone one of the super-powered students known as espers. High-ranking master of electricity Mikoto Misaka laughs off these stories until she comes face to face with a copy of herself. The duplicates are real, and are being mass-produced from Misaka's DNA, making each one of them a little piece of her. These clones - her sisters - are being systematically murdered in a series of experiments designed to turn a sadistic killer into the strongest esper in history. Misaka vows to save her copies and destroy the project, but this might be one fight she can't win alone.